On-demand services (e.g., a taxi hailing service) utilizing Internet technology have become increasingly popular because of their convenience. For a specific user, a system providing on-demand services may present recommendations (e.g., a possible friend, a travel recommendation) to the user based on the user's location and preference. In some situations, in order to provide appropriate and interesting recommendations, it is desirable to know the level of connection (affinity) between the users. The systems and methods herein disclosed may at least in part be used to determine the affinity between the users.